The explosion characteristics of the insulating oil under unconfined conditions and its damage assessment

Abstract

With the application of ultra-high voltage (UHV) technology, a substantial amount of energy released from an internal arc fault in the transformer leads to the instantaneous decomposition of insulating oil into various flammable gases. This results in a rapid increase in internal pressure, making it highly probable for the transformer casing to rupture. Consequently, the insulating oil and its decomposition products disperse in the air, which in the presence of an ignition source, can trigger an explosive accident. To reveal the explosion characteristics of insulating oil, experiments and simulations are conducted under unconfined conditions. Besides, a quantitative explosion risk assessment is conducted. The results indicate that, at 20 ms, a high temperature and strong turbulence region appears at about 0.9 m from the center of the cloud and 0.7 m in height, and the combustible cloud is initiated near the region. The safety distances for humans free from the hazard of shock waves are 11.79 m, 13.74 m, and 21.63 m with the amount of insulating oil of 10 L, 15 L, and 20 L, respectively, and the safety distances for humans free from the hazard of thermal radiation are 21.2 m, 26.4 m, and 29.2 m respectively.